Method of fluid degassing

ABSTRACT

A method for effectively removing gas entrained in a viscous drilling fluid involves pumping the fluid with an open-center impeller pump and thereby creating a central opening in the pumped fluid into which freed gas can move coaxially with the pumped fluid; emitting the fluid in a continuous radial spray against the inner surface of the wall of a spray vessel while simultaneously creating a vacuum in the spray vessel; communicating the created vacuum area in the spray vessel with the central opening in the pumped fluid to improve gas removal and pumping efficiency in the pump; flowing the pumped fluid into an enclosed flow trough having a fluidic barrier at each end; and conducting the removed gas from the flow trough to a safe disposal area.

BACKGROUND OF THE INVENTION

The present invention relates to the art of drilling fluid processing,and more particularly to a system for degassing drilling muds. Thepresent invention provides a centrifugal pump system for pumping gasladen drilling fluids while restricting the flow of gases removed fromsuch liquids to conduits by which they are carried to safe disposalareas. Such a centrifugal pump system is desirable for the transfer ofsuch gas laden fluids into degassing or deaerating vessels, or out ofsuch vessels during periods of incomplete degassing.

In drilling a well for oil, gas and the like, the drilling bit issupported in the well bore by tubing. The tubing is hollow pipe composedof a plurality of individual lengths of pipe connected together. Thetubing carries drilling fluid in its interior down to and through thedrilling bit. The drilling fluid at the bottom of the well bore passesupwardly in the annulus between the exterior surface of the tubing andthe interior surface of the well bore to the surface of the earth andthen through a return pipe to storage pits on the surface of the earthcommonly referred to as mud pits.

The drilling mud is ordinarily an aqueous suspension of solid mattergenerally containing minerals such as bentonite and barite. The drillingmud lubricates and cools the drill bit and serves as a carrier towithdraw drill cuttings and debris from the well for disposal. Thedrilling mud also provides a pressure seal in the well bore to preventthe escape of gases from the well. The pressure exerted by the column ofdrilling mud normally is greater than the pressure which may be releasedupon encountering gas pockets as the well is drilled. The column ofdrilling mud counteracts gas pressure and prevents blowouts but veryoften becomes contaminated with the gases encountered during thedrilling operation.

Under many circumstances it is desirable and in fact often absolutelyessential that the gases be removed from the drilling mud andtransmitted to a disposal area. Since it is economically unfeasible todiscard the contaminated drilling mud and because of the danger of thegases in the mud being released into the atmosphere in large quantitiescreating dangerous conditions at the drill site, it is necessary toprocess the mud to remove the gases and recirculate the degasseddrilling mud through the borehole. The contaminating gases may bepoisonous or highly explosive and the release of such gases into theatmosphere would present a substantial risk to personnel in the drillingarea. The presence of gases in the drilling mud decreases its weight andaffects its viscosity often rendering it unsuitable for recirculationthrough the borehole. When gases are contained in the drilling mud beingcirculated through the borehole, it increases the danger of a blowout inthe well.

A "Notice to Lessees and Operators of Federal Oil and Gas Leases in theOuter Continental Shelf, Gulf of Mexico Area" was released May 7, 1974by the United States Department of the Interior Geological Survey, Gulfof Mexico Area, relating to hydrogen sulfide in drilling operations. Thenotice outlines requirements for drilling operations when there is apossibility or probability of penetrating reservoirs known or expectedto contain hydrogen sulfide. Section 3. f. provides that "drilling mudcontaining H₂ S gas shall be degassed at the optimum location for theparticular rig configuration employed. The gases so removed shall bepiped into a closed flare system and burned at a suitable remote stack."

The prior art shows examples of systems for the degasification ofdrilling mud, many of which utilize a vacuum tank and some sort ofbaffle arrangement which exposes the drilling mud to vacuum environment,thus causing the entrapped gas to be removed. This is only part of thetask however for serious problems are encountered in the handling ofdrilling muds, particularly in evacuating the drilling mud from thevacuum tank to return it as degassed mud to the well head. Precisecontrol of the rates at which drilling mud enters the vacuum tank,degassed mud leaves the vacuum tank, and gases are evacuated from thetank, is necessary in order to produce an acceptable product at thenecessary rate.

Some systems of the prior art use a separate vacuum pump and oftenexpose this apparatus to the possibility of ingestion of drilling muds,a situation which normally damages the pumping mechanism and, at thevery least, forces the entire system to be shut down for cleaning. Priorart devices have also exhibited problems in matching the vacuum pulledon the vacuum tank with the flow requirements of the entire system,which may be continually changing.

Numerous efforts have previously been made to eliminate the use of a mudjet for effecting the flow of mud such as substituting a centrifugalpump for the mud jet. However, such previous efforts have not beenentirely successful inasmuch as a pump tends to become air-locked whenthe supply of mud to the tank is insufficient, or when vortexing of mudin the tank permits air or gas to enter the pump or when air or gas ispresent in the mud for any reason. Even when self-priming centrifugalpumps are used, several minutes may elapse before the pump resumeseffective pumping action and during that period the efficiency of thedegassing operation in the tank is materially affected. Previousattempts to provide vapor-vented centrifugal pumps include thatdisclosed in U.S. Pat. No. 2,815,717 which is not practical in abrasivefluids such as drilling muds because of rapid wear on its seals. Adesign disclosed by U.S. Pat. No. 3,769,779 avoids the abrasion of sealsbut requires the freed gas to flow counter to the incoming fluid at oneor more points.

DESCRIPTION OF PRIOR ART

In U.S. Pat. No. 3,769,779 to Walter E. Liljestrand, patented Nov. 6,1973, an apparatus is shown for degassing fluids, particularly drillingmuds, comprising a vessel having an inlet and an outlet for the intakeand discharge of the fluid to be treated, a centrifugal pump connectedto the vessel for circulating the fluid through the vessel and means forremoving gas from the region of the impeller means in the centrifugalpump. The invention also includes a centrifugal pump designed forhandling gas laden fluids, the pump having a means for removing gas fromthe region of the pump impeller. The invention further includes acentrifugal pump for handing corrosive and/or abrasive fluids whereinsaid fluids are prevented from contacting the pump seal by means of agas pressurized compartment adjacent the seal.

In U.S. Pat. No. 3,616,599 to Gerald E. Burnham, patented Nov. 2, 1971,a drilling mud degasification apparatus is shown having baffle plates ina vacuum tank over which thin films of mud are degassed as they flowdownward to a receiving area of the tank. Venturi-type dual ejectorapparatus is located in a sump in the tank to remove degassed mud and todraw a vacuum on the upper portion of the tank.

In U.S. Pat. No. 3,241,295 to Phil H. Griffin, III et al, patented Mar.22, 1966, a mud degasser apparatus combination is shown with a muddegasser vacuum tank having a mud inlet and a mud outlet for continuousflow of mud through the tank, means for maintaining the interior of saidtank at sub-atmospheric pressure, valve means provided in said mud inletfor controlling the rate of flow of mud into the tank, means responsiveto variations of level of mud in said tank for varying thesub-atmospheric pressure in the tank, and means responsive to variationsof pressure in the tank for opening and closing said valve means.

In U.S. Pat. No. 3,249,227 to Alfred B. Long, patented May 3, 1966, acentrifugal separator is shown for the treating (mechanical processing)of slurries, and for the classification by specific gravity of solids inslurries and muds, of components of emulsions, and also for thedegasification of drilling muds. It is suitable for use in the chemical,mining, and petroleum industries.

In the publication "A Degasser You Can Understand" by Walter E.Liljestrand, presented at IADC Rotary Drilling Conference in March 1974,a description of mud degassing is set out. A degasser is one of severalimportant components necessary on a rig to handle gas in mud. This papergives perspective to the whole problem. The atmospheric degasserdescribed is entirely new in concept. The flow is controlled by theliquid and the pump.

SUMMARY OF THE INVENTION

The present invention provides a system for the degasification ofdrilling mud in a continuous manner as the mud is circulated to and froma well head. The present invention provides a centrifugal pump degassingsystem capable of pumping gas laden liquids, including drilling fluids,while restricting the flow of gases removed from such liquids toconduits by which they are carried to safe disposal areas. Such acentrifugal pump degassing system includes the transfer of such gasladen fluids into degassing or deaerating vessels, or out of suchvessels during periods of incomplete degassing.

One embodiment of the centrifugal pump degassing system of the presentinvention includes a hollow centered impeller driven by a hollow shaftthrough which the gas may be withdrawn without having to move through afluid filled zone. A prerotation inlet chamber below the impeller admitsdrilling mud into the impeller housing in a peripheral flow with thereleased gas flowing from the vortex of the chamber and the impellerthrough the hollow drive shaft and into a conduit which leads directlyinto the degassing vessels. The impeller shroud gives the drilling mudadditional rotational velocity through a reduced radius, furtherestablishing a central vortex toward which any gas escaping from thefluid will be forced by the mud up the hollow impeller shaft. Releasedgas flows in the same axial direction through the pump as the mud. Thedrilling mud exits the impeller housing through the exit port and movesin response to the pump pressure into a cylindrical vessel where it isemitted in a radial spray pattern against the wall of the vessel. Acentral opening in the spray pattern is maintained which communicatesthe vessel above the spray pattern to that portion of the vessel belowthe pattern. The spray pattern preferably impinges on the full peripheryinside the vessel and this pattern provides advantages not realized inother spray configurations.

The foregoing and other objects and advantages of the present inventionwill become apparent from a consideration of the following detaileddescription of the invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a degassing system constructed in accordance with thepresent invention.

FIG. 2 is an enlarged view, partly in section, showing the centrifugalpumping means from the system shown in FIG. 1.

FIG. 3 is an enlarged view, partly in section, of the spray vessel.

FIG. 4 is a partial cross-sectional side view of the gas separationtrough.

FIG. 4a is an enlarged view of a portion of the structure shown in FIG.4.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and, in particular, to FIG. 1, anembodiment of a degassing system constructed in accordance with thepresent invention is illustrated. Gas contaminated drilling mud 22 frommud tank 20 is directed to a mud spray vessel 29 through line 24 by apump system 14. A vacuum created in vessel 29 is communicated by conduit25 to a top cap 12 with a rotatable seal on the top end of the hollowpump shaft of pump 14. Mud is pumped via line 24 through the wall ofvessel 29 and is sprayed outward through spray head 27 where it impingesthe wall of vessel 29 and moves downward, out the bottom discharge tube23. From tube 23 the mud passes into the gas separation trough 28 andflows down the trough under a float-operated gate 58, down the returnpipe 30 and back into degassed mud tank 21.

The pumping system 14 of this invention provides a centrifugal pumpcapable of pumping the gas laden drilling mud 22, while restricting theflow of contamination gases removed from the drilling mud to conduit 25,by which they are conveyed via vessel 29, trough 28, and conduit 26 tosafe disposal areas. The pumping system 14 transfers the gas ladendrilling mud into the spray vessel 29.

It is well known that conventional centrifugal pumps tend to becomevapor locked which seriously reduces the volume capacity of the pumps,limiting their effectiveness in handling fluids. Previous attempts toprovide vapor-vented centrifugal pumps include that disclosed in U.S.Pat. No. 2,815,717 which is not practical in abrasive fluids such asdrilling muds because of rapid wear on its seals. The design disclosedby U.S. Pat. No. 3,769,779 avoids the abrasion of seals but requires thefreed gas to flow counter to the incoming fluid at one or more points.

As can be better seen in FIG. 2, the pumping system 14 of the presentinvention uses a hollow centered impeller 2 driven by a hollow shaft 3through which the gas may be withdrawn without having to move through afluid filled zone. A prerotation inlet chamber 8 and shroud 7 below theimpeller 2 admit free fluid into the impeller housing 4 in a peripheralflow. Released gas flowing from the vortices of chambers 7 and 8 and ofthe impeller 2 moves upward through the hollow drive shaft 3, thencethrough the top of the shaft into a top cap 12 which has dynamic seals12a therein for sealing engagement with the rotating shaft.

The centrifugal pump includes an impeller 2 rotatably mounted on shaft 3and made to rotate in impeller housing 4 by a motor 5 driving the shaft3 through a sheave 6a and belt drive 6. A shroud section 7 and aprerotation inlet section 8 are attached to the impeller housing 4.Fluid enters the prerotation inlet section 8 through essentiallytangential entrances 9, giving the fluid a circular motion in thedirection of rotation of impeller 2. The fluid must then pass throughthe shroud section 7 to reach the impeller and in so doing it is givenadditional rotational velocity by the reduced radius, furtherestablishing a central vortex through which any gas escaping from thefluid will be released toward the central longitudinal axis of the pumpshaft and up the shaft. The released gases rise through the centralopening 10 in impeller 2, through the hollow center 11 of shaft 3, tothe conduit 25 in top cap 12.

Fluid under pressure from the impeller rotation exits the impellerhousing through port 19 but is also free to enter the space betweenimpeller 2 and the top 16 of housing 4 and into the annular space 17between the shaft 3 and shaft housing 15. When the impeller is not inmotion, the fluid level in the annulus 17 will be that of the externalfluid, but when impeller is turning the pressure developed could forcethe fluid somewhat higher in the annulus 17. To prevent such rise, adischarge tube 18 may be provided through which such pressure can berelieved by venting the small flow of fluid which may migrate upwardthrough space 17. Also, a double helical vane 37 may be affixed to theoutside of the impeller shaft 3 to provide a downward impetus on anyflow of fluid up the annulus 17, or an annular dynamic seal could belocated between shaft 3 and housing 15.

Referring now to FIG. 3, the spray vessel is illustrated incross-section. The vessel 29 generally comprises a cylindrical uppersection 29a, a frustoconical intermediate section 29b and the bottomdischarge tube 23. The mud inlet line 24 is attached to a transmitcollar 32 which is sealably secured in the wall of vessel 29. A topcover plate 33 is sealingly secured to the upper section 29a by meanssuch as bolts 34 passing through flange 35. An upper discharge pipe 36communicates with an opening in plate 33 and has connected thereto thegas flow conduit 25.

The spray assembly 27 is suspended in a generally central locationinside vessel 29 by means of an inlet conduit 40 which in turn isattached to collar 32 in coaxial alignment therein. Assembly 37generally comprises an outer annular flow bowl 38 which generallyincludes a double-walled cylindrical member closed at the bottom andopen at the top. The enclosed area 39 formed by the two walls and bottomof bowl 38 is in fluid communication with flow line 24 via collar 32 andinlet conduit 40.

A deflector plate 41 is located directly above annular space 39 and inclose proximity to bowl 38. The location of plate 41 with respect tobowl 38 forms a relatively narrow spray gap 44 therebetween. Plate 41preferably is of a larger diameter than bowl 38 to prevent fluid sprayfrom going upward in vessel 29. The plate has a central opening in whichis secured a cylindrical center spool 42 which in turn fits inrelatively close-fitting relationship inside the central space of bowl38.

Center spool 42 has an open passageway 43 passing therethrough. Thecenter plate and spool arrangement is supported by a threaded boltmember 45 which is threadably engaged at its lower end in a cross membersupport 46 and at its upper end in a similar cross member support 47.Cross member 47 extends across bore 43 and is attached to plate 41 ateach end of the cross member by means such as welding or bolts.Likewise, cross member 46 extends across opening 43 and is attached ateach end to the bottom of bowl 38 by means such as welding.

Adjustment of spray gap 44 is obtained by rotating plate 41 clockwise tonarrow gap 44 or counterclockwise to widen gap 44. The rotation of plate41 also rotates threaded cross member 47 which moves the plate and crossmember up and down on the threaded bolt 45.

FIG. 4 is an enlarged cross-section of the gas separation trough 28.This primarily consists of an elongated enclosed flow trough 50connected to an inlet cabinet 51. The inlet cabinet has at the top aninlet conduit 52 having an annular flange 53 at the top thereof. Acorresponding matching flange 48 is located at the bottom of thedischarge tube 23 of vessel 29.

The matching flanges 48 and 53 allow placement of vessel 29 atop trough28 where it may be attached by means such as bolts passing through thecomplementary flanges. The inlet tube 52 is in coaxial alignment withdischarge conduit 23 and extends through a substantial portion ofcabinet 51 to a point near the bottom thereof. An alternate location forconduit 52 is drawn in phantom at 55 for configurations where height ofthe assembly is limited.

A vertical baffle plate 54 is attached to the bottom of cabinet 51 andextends entirely across the cabinet from one side to the other. A secondplate 72 extends downward from the top of the trough to a point abovethe bottom of the trough, forming a flow space thereunder. A peaked roof56 is hingedly attached to channel section 50 and completely closes thissection of the trough.

The inlet cabinet 51 is also completely closed. A discharge port 57 islocated near the end of channel section 50 and is in communication withmud return pipe 30. A flow control plate 58 is secured to float arm 61which is hingedly attached at 59 to the far end 60 of the trough. Theplate extends substantially across the width of the trough and islocated forward of port 57.

A float member 62 is secured to the opposite end of arm 61 fromconnection 59. An enclosure plate 66 is secured to the back 60 of thetrough and extends forward over discharge opening 57. A downwardextending front plate 67 is attached to the front edge of plate 66 inclose sliding relationship with control plate 58. Plates 58, 66, and 67preferably extend substantially across the width of trough 28. Acheckvalve 68, which can be of any of the many known one-way valves, maybe provided on plate 66 to allow discharge of gas trapped therebelow.

FIG. 4a illustrates one type of checkvalve which can be used in plate66. In this instance, a hinged damper valve 69 is pinned to plate 66 bypin 70 such that it is arranged to rest in a closing position on port 71which passes through plate 66. Gas pressure below plate 66 can moveupward through port 71, lifting valve 69, and moving into the upperportion of trough 28. Gas or fluid flow downward through port 71 isprevented by the closing of damper 69.

It should be noted that the action of the gate assembly comprising float62, arm 61, and plates 58, 66, and 67, is to ensure a fluidic sealbetween trough 28 and discharge port 57 in order to provide a barrier tothe passage of gas through port 57. As a further means of preventing gasflow through port 57, discharge conduit 30 may be extended upward apredetermined distance past the bottom of trough 28. This distance couldbe selected to locate the top of conduit 30 higher than the bottom ofplate 67.

A gas discharge tube 63 passes through the peaked roof 56 and hassecured thereto a gas flow line 26. One or more vertical baffles 64extend across a substantial portion of the width of the trough 28 andextend downward into the trough towards the bottom thereof. These may bewelded or secured to the sides of the trough and are open in the peakedroof section 56. Roof section 56 in one embodiment had a slope of 45°with the peak being located generally centrally along the roof section.

In typical operation, the mud gas separator assembly of this inventionmay be assembled at a well drilling site and placed on the mud tanks 20and 21 by means such as extended cross member pipes 65 which are ofsufficient length to span the width of the tank 20. The motorized pumpassembly may also be suspended from the side of the tank by hanger meansor other means known in the art. The drilling fluid is pumped into thetank 20 from the drill site preferably through a device which removessolids such as rock cuttings and sand from the drilling mud.

The pump motor is started and fluid is drawn into the tangential inlets9 in chamber 8 and upward through shroud 7 whereupon it is expelledthrough discharge port 19 by impellers 2.

A central vortex is formed in the center of the hollow impeller memberat 10 and gas bubbles which become separated from the mud in thecentrifugal pump are moved inwardly into area 10 by the action of theheavier mud being moved outward in response to the centrifugal forcesimposed on it by the pump impeller. The separated gas moves upwardthrough the hollow center 11 of shaft 3 and out through the top of thehollow shaft which is sealingly covered by the top cap 12.

The pumped mud moves out discharge port 19 into conduit 24 and thenceupward into spray vessel 29. At spray vessel 29, the mud moves throughcollar 32 into the conduit 40 and the annular space 39. The highpressure mud is forcefully emitted through narrow gap 44 againstdeflector plate 41 forming a circular spray outward from plate 41against the inside surface of the outer wall of vessel 29. This spray offluid forms a "doughnut" shape having an open central portion at 43.

The action of the spray outward against the wall of the vesselestablishes a strong vacuum in the upper portion of the vessel above thespray. The action of the fluid against plate 41 serves to place thefluid in high turbulence and shear which results in a combining of manysmall entrained gas bubbles into larger bubbles. The reason for thecreation of the high vacuum in the upper part in the chamber appears tobe a result of the venturi effect of the spray outward and the opencentral passage 43.

This creation of a high vacuum is very beneficial to drawing the smallbubbles in the fluid together and out of the fluid. The vacuum is alsobeneficial by its effect on the centrifugal pump 14. The vacuumcommunicates with the pump 14 through conduit 25. This action serves tofurther draw off the gas separated in the pump at the central opening10. The vacuum further enhances the efficiency of the pump by reducingthe so called vapor lock and cavitation effects in the impeller area andby further aiding in the intake of fluid into the pump as a result ofthis vacuum.

Thus, the created vacuum in the upper portion of vessel 29 is amulti-purpose advantage. It aids in the combination of small bubblesinto large bubbles; it aids in drawing the entrapped gas bubbles fromthe fluid both in the vessel 29 and in the impeller area of the pump 14;and it further increases the efficiency of the centrifugal pump in oneor more ways.

The mud is emitted through spray gap 44 in a continuous sheet andimpinges on the wall of vessel 29, and flows downward therealong untilit reaches the discharge tube 23 from which it passes into the intake 52of the separator trough. The fluid flows downward to the bottom ofcabinet 51, back upward over the top of flow baffle 54, and then downagain under plate 72. Plates 54 and 72 prevent open communication fromthe upper portion of channel 50 to the vessel 29. This results in amaintenance of the high vacuum in vessel 29.

Were plates 54 and 72 to be removed, an open communication of the vacuumarea of vessel 29 would be permitted with the discharge line 26, and thevacuum would be greatly reduced. Thus, the placement of the bafflescreates narrow openings at the top of the cabinet and the bottom whichgenerally are filled by the flow of fluid from conduit 52, thuseffectively forming a liquid seal and so preventing open gascommunication therepast.

Small gas bubbles are combined in vessel 29 to form large bubbles whichpass through conduit 52 in the drilling fluid over baffle 54, underplate 72, and into the trough section. Although the bubbles are still inthe fluid, they have been enlarged by having been combined through theturbulence and vacuum effects in vessel 29 to the point where they havesufficient buoyancy to rise to the top of the fluid stream in theenclosed trough section 50. The baffles 64 slow transit of the foamyupper level of fluid containing the highest concentration of gas bubblesin order to allow them more time to break out of the mud.

The entire operation of the degassing system depends in large part uponcombining the small entrapped gas bubbles into larger bubbles so thattheir total buoyance is sufficient to overcome the inertia and viscosityof the heavy fluid in which they are entrapped. The operation of thepresent invention is advantageous in that the discharge gas whichcollects at the top of the trough section 50 is under a net positivepressure and therefore flows freely from the trough section through hose26 without need for mechanical removal means such as a vacuum pump orfan.

The resulting positive gas pressure in trough section 50 apparently is aresult of the hydrostatic head of the fluid in vessel 29 acting throughthe entirely enclosed vessel 29 and trough 28. An optimum level of fluidin the trough is maintained by gate 58 which preferably is connected toan adjustable float member 61 for maintaining the predetermined fluidlevel.

It should also be pointed out that one of the important parametersinvolved in the gas separation process is the time of transit of thefluid through the separation trough. A trough of insufficient length forthe given flow velocity of the drilling fluid therethrough will notallow sufficient time to accomplish an acceptable gas separation ratebecause of the lack of time for the smaller bubbles to overcome thefluid inertia and viscosity and rise to the surface.

It was found in one particular embodiment that a trough length ofapproximately eight feet provided a gas removal rate of around 85percent in a test slurry pumped at 400 GPM. Any additional length willprovide small increases in the percentage of gas removed from the fluid.Additional methods of increasing the residence time of the fluid in theseparation trough include lowering the pumping rate, increasing thecross-sectional flow area of the trough, and altering the depth of thedrilling mud maintained in the trough.

Thus, it can be seen that with the present invention, many advantagesare obtained in the degasification of the drilling mud. One of theseadvantages involves eliminating the need for a mechanical vacuum pump orblower device to remove the possibly dangerous gases from the separatorassembly. Another advantage obtained involves the much greater pumpingefficiency of the centrifugal pump arising from the application of thevacuum to the impeller vortex area. Another advantage gained is captureof the removed gases from the pump vortex area and the conveyance ofthese gases to a section of a vessel where they can be captured andflowed to a safe disposal area.

Further advantages involve the more efficient combining of small gasbubbles into the more easily removable large bubbles as a result of thehigh vacuum formed in the spray vessel and the more effective removal ofbubbles as a result of the efficient design of the separator trough.Other advantages not discussed herein or readily apparent from thedescription above are obtainable with the practice of this invention.

Although a specific preferred embodiment of the present invention hasbeen described in the detailed description above, the description is notintended to limit the invention to the particular forms of embodimentsdisclosed therein since they are to be recognized as illustrative ratherthan restrictive and it will be obvious to those skilled in the art thatthe invention is not so limited. For instance, whereas the spray vessel29 has been described as a cylindrical vessel, it is obvious that onecould substitute other configurations for this vessel such as square,rectangular, oval, etc. Also, whereas a centrifugal impeller type pumpis utilized with this invention, it is clear that other types of fluidpumping apparatus would be workable with this invention. Also, whereasthe mud gas separator trough 28 has been described as a rectangularvessel having an elongated flow channel with a peaked roof, it isobvious that other cross-sectional configurations of this trough couldbe utilized as a U-shaped trough or a circular trough. A furthermodification would involve providing a gas conduit from the upperportion of vessel 29 to the lower portion of the vessel in lieu ofcommunication through a central opening 43 in spray assembly 27. Thus,the invention is declared to cover all changes and modifications of thespecific example of the invention herein disclosed for purposes ofillustration which do not constitute departure from the spirit and scopeof the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method of removing asubstantial amount of entrained gas from a viscuous fluid such asdrilling mud, said method comprising:introducing the fluid into a fluidpump and pressurizing the introduced fluid; discharging the pumped fluidthrough a conduit and into a spray vessel; spraying the fluid outwardfrom a deflector in the spray vessel in a 360° radial spray patternhaving a central opening; creating a vacuum in the spray vessel by saidspraying step; flowing the sprayed fluid into a discharge outlet of thespray vessel; discharging said fluid into a closed degassing vessel;moving said fluid through an extended length of the degassing vesselwhile maintaining a fluidic barrier to gas flow between the extendedlength of the degassing vessel and the spray vessel; and, dischargingthe fluid from the degassing vessel and collecting the gas removed fromthe fluid in the degassing vessel.
 2. The degasification method of claim1 further comprising communicating the created vacuum in the sprayvessel to the fluid pump to further remove gas from the fluid in thepump, prevent pump vapor-lock, and increase the intake of fluid into thepump.
 3. The degasification method of claim 1 further comprising thestep of retarding the flow rate of the upper level of fluid flow throughthe degassing vessel.
 4. A method of removing small and large entrainedgas bubbles from viscuous fluid and collecting the removed gas for safedisposal, said method comprising:locating in the fluid the intake portof a fluid pump; inducing fluid into the intake port by operating thefluid pump; simultaneously creating an open vortex in the pumped fluid;discharging the pumped fluid into a discharge conduit; introducing thepumped fluid from the discharge conduit into a spray vessel; sprayingthe pumped fluid against a deflector plate in the vessel in such amanner as to create a suction in the upper portion of the spray vesselrelative to the atmospheric pressure outside the vessel; communicatingthe pump vortex area with the upper portion of the vessel; flowing thefluid from the vessel through an enclosed conduit into an encloseddegasser tank while maintaining a fluidic barrier between the open areasof the vessel and the tank; moving the fluid through the tank whileretarding the flow of the upper layer of fluid; discharging the fluidfrom the lower portion of the tank and the removed gas from the upperportion of the tank into predetermined discharge outlets.
 5. A method ofremoving entrained gas bubbles from a fluid for safe disposal,comprising:locating in the fluid an intake port of a fluid pump; drawingfluid into the pump by operating the pump; discharging the pumped fluidinto a discharge outlet; communicating the discharge outlet with anenclosed spray vessel; emitting the fluid into the spray vessel againsta deflector member to force small bubbles of gas to combine into largerbubbles; flowing the fluid out of the spray vessel through a conduitinto an enclosed flow vessel; maintaining the flow vessel partiallyfilled with flowing fluid and retarding flow of the upper level of thefluid to aid in removing entrained gas bubbles therefrom; collecting inthe upper portion of the flow vessel a substantial portion of theremoved gas bubbles; removing the collected gas to a safe disposal area;and, discharging the degassed fluid from the lower portion of the flowvessel.
 6. A method of degassing drilling fluid comprising:locating inthe drilling fluid a centrifugal, impeller-type pump having intake meansand discharge means and a hollow drive shaft driving the impeller;inducting fluid into said pump through said intake means by rotatingsaid shaft and impeller while simultaneously maintaining an open centralvortex in the fluid in the impeller section; pumping the fluid throughthe discharge means into an enclosed spray vessel and against adeflector plate, sheet forming a radial spray against the vessel wall,while maintaining communication from the vessel area below the spray tothe vessel area above the spray; communicating the upper portion of thespray vessel with the hollow drive shaft; flowing the fluid downward outof the bottom of the spray vessel through an enclosed conduit into anenclosed trough located therebelow and connected to said conduit;flowing the fluid through a restricted opening in the trough to form abarrier to open gas communication between the trough and the sprayvessel; flowing the fluid down the trough length a sufficient distanceto allow a substantial amount of the gas to bubble out of the fluid;and, discharging the fluid and the removed gas from respective fluid andgas discharge outlets in the trough.
 7. A method of removing entrainedgas bubbles from a fluid, comprising:flowing the fluid by gravity flowinto an inlet conduit in an elongated flow trough; flowing the fluid bygravity flow past a liquid seal barrier near the inlet, therebypreventing communication of gas pressure from the trough through theinlet; flowing the fluid down the elongated trough while retarding theflow of the upper level of fluid; collecting freed gas bubbles in theupper portion of the trough and removing them through a gas discharge;flowing the fluid past a second liquid seal barrier and into a dischargeconduit.
 8. A method of introducing shear into a fluid containingentrained gas bubbles to aid in combining small bubbles into largebubbles, while simultaneously creating a beneficial vacuum thereabove,said method comprising:locating a radial spray assembly inside a closedspray vessel; introducing the fluid under pressure into the sprayassembly and emitting the fluid outward in a continuous sheet of radialspray against the vessel wall; providing gas communication from thevessel area below the spray to the vessel area above the spray; and,discharging the fluid from the spray vessel.
 9. The method of claim 8wherein said emitting step comprises forcing the fluid out a circularannular gap against a deflector plate in close proximity thereto.
 10. Amethod of combining small entrained gas bubbles in a fluid into largebubbles, said method comprising:pumping the fluid through a centrifugalimpeller pump having a hollow shaft; forming an open central vortex insaid fluid in said pump communicating with the bore of the hollow shaft;pumping the fluid from said pump into a spray assembly in a closedvessel; emitting the spray radially outward in a continuous sheetagainst the inner wall of the vessel; providing gas communication fromthe vessel area below the radial spray to the vessel area above thespray; and, communicating the upper portion of the vessel to the bore ofthe hollow shaft.